NUCLEAR ASTROPHYSICS AT LABORATORI

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Silvio Cherubini for ASFIN2 20 November 2012

NUCLEAR ASTROPHYSICS AT LABORATORI

NAZIONALI DEL SUD

ITALY – JAPAN 2012

Milano, 20-23 November 2012

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NUCLEAR ASTROPHYSICS

@

CATANIA

LABORATORI NAZIONALI DEL SUD

Silvio Cherubini CNS-The University of Tokyo RIKEN Campus, Wako Dec 17^th , 2009

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→ Nuclear Astrophysics and Indirect Methods

→ Recent applications of THM

¹⁸

F+p and

¹¹

B(p, a )

→ VERY Recent application of VNM

→ Non-THM applications (Big Bang,

¹⁶

N b- delayed alpha decay)

Summary

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History of Nuclear Astrophysics in short!

- Eddington, Aston, Gamow, Bethe: “energy production in stars” (1920-1939) - Gamow introduced the Gamow factor (1928), convoluted with the Maxwell distribution this fixes the typical energy for nuclear reactions in stars

Reaction rate: r = N₁N₂v (v)

(# reactions volume^-1time^-1) exp(-2ph)

exp(-E/kT)

- B²FH: kind of formal definition of nucleosyntesis in stars (1957)

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GAMOW WINDOW  10-100 keV (non esplosiva)

Nano- Picobarn (even less!)

Miserable S/N ratio

Estrapolation

Dedicated Experiments / Lab (LUNA)

Electron Screening

Estrapolation…

Indirect Methods (CD, ANC,

THM

⁾

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THM: a primer

=Trojan Horse nucleus

E_BA > E_C

E_C

S x x x

B

S A

Nuclear field

E_C= Coulomb barrier between A and B E_BA= relative energy between A and B

E_Bx= E_CD – Q₂ E_Bx= interaction energy B-x

Electron screening

removed by construction

C D

x

Idea: get the 2-body cross-section of the process

B + x → C + D

At astrophysical energies from the QUASI-FREE contribution of a 3-body reaction (C. Spitaleri, Folgaria 1990)

B + A → C + D + S

S

A = x  S

18

F+p

¹⁵

O+ a

18

F+d

¹⁵

O+ a +n

d = n  p

P C P

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d³σ

3-body Reaction Virtual Decay Virtual reaction

(astrophysical process) A

B

S C D

x

=

^A

x

S



x

B D

C

Assuming that a Quasi-free mechanism is dominant one can use the PWIA:

E_Bx= E_CD-Q_2b dΩ_C dΩ_DdE_cm

 KF·|Φ (P

_s

)|

²

^

_dΩ^dσ^N

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Measured at high energy

Calculated e.g.

Montecarlo d³σ

3-body Reaction Virtual Decay Virtual reaction

(astrophysical process) A

B

S C D

x

=

^A

x

S



x

B D

C

E_Bx= E_CD-Q_2b dΩ_C dΩ_DdE_cm

KF·|Φ (P

_s

)|

² _dΩ^dσ^N

Indirectly Measured

/ 

Assuming that a Quasi-free mechanism is dominant one can

use the PWIA:

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APPLICATION OF THE METHOD and tricky points

From the theoretical/phenmenological point of view

1. Selection of the three body reaction and of the Trojan Horse Nucleus depending on its cluster structure properties. This

affects the number and type of reaction mechanisms competing with the QF one and the cross section value of the QF channel itself (more in two slides)

2. Check of the presence/dominance of the QF mechanism (impulse distribution reconstruction, study of the angular distribution, Treiman-Yang criterion)

3. Reliability of the “ingredients” used in d² derivation, e.g. of impulse distribution of the THl nucleus.

4. If one is measuring a cross section below the Coulomb barrier,

then has to correct the THM x-sec for penetration factor before comparing the THM results with the direct ones.

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From the experimental point of view:

1) Optimization of the energy and angular resolution of the

experiment to obtain the necessary resolution in the E_xB variable (relative energy of x-B (related to the cm energy of the

astrophysical process)

2) Background noise suppression (this is not THM specific...) including the PHYSICAL background (see next slide)

3) Avaailability of direct measurements (above the region where Electron Screening effects start to show up and if possible also above the Coulomb barrier).

D E

_xB

= f( D E

_C

D E

_D

Dq

_C

Dq

_D

)

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PHYSICAL BACKGROUND: an example

6

Li+p →

³

He+

a

from

⁶

Li+d →

³

He+

a 

n

Art of the TH: finding the phase space region where this diagram is dominant!

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ADVANTAGES of the Method

1) The cross sections in the experiment are typical QF processes ones (mbarn/sr) though one is measuring a nuclear reaction at astrophysical energies

2) The THM x-section is purely NUCLEAR: no suppression effect due to Coulomb barrier

3) No electron screening effect: one can get INDEPENDENT pieces of information on the electron screening potential by comparison with direct data

4) The experimental setup is tipically simple enough

5) The THM can be extended to use QFR in studying NEUTRON induced reaction (VNM Virtual Neutron Method)

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18

F+p 

¹⁵

O + a AT CRIB VIA THM

18

F+d 

¹⁵

O + a + n

Thick target method (also at CRIB) Indirect methods

Transfer reaction

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For the star energetics this are peanuts!

18

F(p,

a

)

¹⁵

O

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STATE OF THE ART

DIRECT EXPERIMENT

TRIUMF DATA

C. E. Beer et al. PHYSICAL REVIEW C 83, 042801(R) (2011)

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18/03/2013 16

THM Experiment kinematics… needs all!

n_Spectator

A

B

S c d x

2H

18F ⁴He

15O

p E(¹⁸F) = 50 MeV

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17

CRIB setup

1. Two beam production tests performed ( Nov . 2005, June 2006) 2. 3*10^5 pps obtained, 10^6 pps within the capabilities of the machine 3. Beam purity > 98%

4. Normalization and deffinitionof the beam particle by particle (PPACs)

BEAM PRODUCTION AT CRIB

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18

EXPERIMENTAL SETUP

(other then CRIB...)

PPAC MCP

CD2 2

TARGET

DPSSD array

Front view of DPSSD array

DSSSD 0.5 m   9cm

 24cm

Safety disk

ASTRHO:

Array of Silicons for TRojan HOrse

PPAC MCP CD2

particle by particle beam reconstruction

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Experimental setup 3

How ASTRHO looks like in reality

(before PPAC explosion...)

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The Italian-French-Japanese connection

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21

Q-VALUE SPECTRUM

DETECTOR PAIRS:

8-1;7-1 CUTS:

“BEAM”+”THRES.”

+”MULT” +”CORR. TIME”

18F+d¹⁵N+a+p @ q=4.194 VNM+RIB!!!

18F+d¹⁵O+a+n @ q=0.658

18F+d¹⁸O+p+p @ q=0.213

18F+d¹⁸F+p+n @ q=-2.225

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22

EVENT SELECTION

Red : ¹⁸F + d ¹⁵N + a + p Black: ¹⁸F + d ¹⁵O + a + n Blue: ¹⁸F + d ¹⁸F + p + n Green: ¹⁸F + d ¹⁸O + p + p “1”+“2”+“3”

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23

Q-VALUE SPECTRUM

GOOD AGREEMENT with

Q-value expected position (0.658 MeV)

And energy beam profile (exp. Sigma 0.8 MeV)

Previous cuts + Erel-Erel correlation +E-Theta correlation

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24

HINTS FOR QF MECHANISM

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d s

N

/d W

BARE NUCLEUS CROSS SECTION

FIRST TROJAN HORSE MEASUREMENT WITH RIBs !!!

38 keV

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11

B(p,a

₀

)

⁸

Be via

¹¹

B(d,a

₀⁸

Be)n

L. Lamia et al.

among «al.»:

S. Kubono,

Y. Wakabayashi,

H. Yamaguchi

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HULTEN FRESCO

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S(E) by THM

S(E) by THM vs

Direct measurement

 electron screening extraction

U

_e^THM

=472+-160 eV

U

_e^dir

=430+-80 eV

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11/20/2012

V N M:

¹⁷

O(n, a )

¹⁴

C via

¹⁷

O + d  a +

¹⁴

C +p

n

17

O + d

-40<p_s<40 (MeV/c)

-40<p_s<40 (MeV/c) 6

Li + d

Magnifying glass effect

VIRTUAL neutron source

A parasitic experiment

performed @ LNS, Catania E(¹⁷O) = 41 MeV

A dedicated

experiment at ND

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Gulino et al. accepted for publication on PRC Rapid

Communication today!!!

angular distributions

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Univ. Catania and INFN-LNS:

C. Spitaleri, S. C., L. Guardo, M. Gulino, S. Hayakawa, I. Indelicato, M. La Cognata, L. Lamia,R.G. Pizzone, S. Puglia, G.G. Rapisarda, S.

Romano, M.L. Sergi, R. Spartà, A. Tumino CNS, The University of Tokyo:

S. Kubono, H. Yamaguchi, Y. Wakabayashi, D.N. Binh,

RIKEN, Tohoku-, Tsukuba-, Yamagata-, Kyushu- University:

N. Iwasa, S. Kato, H. Komatsubara, S. Nishimura, T. Teranishi CSNSM, IN2P3/CNRS and Université Paris Sud:

A. Coc, N. de Séréville, F. Hammache Texas A&M University

R. Tribble, A. Mukhamedzanov, L. Trache RUB: Claus Rolfs

...I apologize with those I surely forgot!

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Direct Measurements and inhomogeneous Big Bang

1H(n,)²H(n,)³H(d,n)⁴He(t,)⁷Li(n,)⁸

Li( a ,n)

¹¹

B

(n,)¹²B(b)¹²C

LINCHPINS OF BIG BANG:

expansion, Cosmic Microwave Background, primordial nucleosynthesis…

BIG BANG SCENARIOS (depending on the phase transition from QGP to Hadronic Universe):

●

HOMOGENOUS Big-Bang

●

synthesis of elements stops at lithium

●

INHOMOGENEOUS Big-Bang

●

much wider set of primordial elements (up to carbon)

●

via the reaction chain:

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+ scintillation beam monitor

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EVERYTHING OK ?

Not really welcome guests…..

1) Leaky ⁷Li beam (no matter what you do, it is there!)

● 2) Neutrons from cyclotron and

● 3) Neutrons primary-beam induced

(really nasty ones)

Can we overcome these problems ?????

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The experimental technique

The principle: we can suppress via

“software” what was not suppressed by the

“hardware” (S. Cherubini)

How?

The Recipe:

1 Apply a tagging procedure to the incoming ⁸Li ions using the MCP pair,

2 use this information to “switch on” the neutron detector only when a ⁸Li has been detected.

This allow for a dramatic reduction of the background neutrons, owing to their de-correlation with the MCP trigger signal Beam time needs (from known X-sec.)

50 ion/sec

^

6 days

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BIG BANG result for ⁸

Li( a ,n)

¹¹

B

^x-sec

500 mbarn +- 170 mbar +- 70 mbarn Stat. Syst.

EPJ A-20, S. Cherubini et al.

+ series of papers

Direct measurements & Inhomogeneous BigBang

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6 ⁸

New runs of BIGBANG were the first experiment at

EXCYT

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BUT the X-sec puzzle remined there...

Inclusive measurements → high Exclusive measurement → low ...

La Cognata et al., The Astrophysical Journal, 706:L251–L255, 2009 December 1

We proposed the following solution to the puzzle

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... contribution from E1 levels at 2418 and -45 keV

--- destructive interference constructive interference

... contribution from E2 level

at -245 keV and direct capture --- destructive interference

constructive interference

C. E. Rolfs & W.S. Rodney Cauldrons in the cosmos

Study of the beta-delayed alpha decay of

¹⁶

N

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“A measurement of the β-delayed α decay of ¹⁶N is considered to be the best method presently available to provide a constrain for the E1 component, SE1 (300), of the ¹² C(α,γ ) reaction”

X. D. Tang et al., Phys Rev C 81, 045809 (2010)

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A view to the level diagram

~10^-5

b^-

levels contributing to E1 component in ¹²C(a,g)¹⁶O

x-sec

NEED TO MEASURE ALPHA DECAY SPECTRUM OF ¹⁶N DOWN TO ENERGIES WHERE THE INTERFERENCE BETWEEN 2418 AND -45 keV

LEVELS (in a-¹²C rel. energies) APPEARS (>1MeV)

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“In a study of the 16N b-delayed decay, three aspects are important:

(1)a particles with energies down to 0.6 MeV have to be detected in coincidence with 12C ions of even lower energies ( 0.1 MeV). Any significant energy loss of the outgoing particles in the catcher foil will deform the shape of the spectrum.

(2) If a particle, emitted from the foil, is stopped in the support frame, only a part of the energy is deposited in the

gas. Such events must be clearly separated from the true coincidence events producing the interference peak.

(3) The detection efficiency must be constant over the energy range from 0.2 MeV to 2 MeV.”

X. D. Tang et al.

Phys Rev Lett 99 052502 (2007) 1), 2) No foil, no frame: NO PROBLEMS

3) Monitor the energy response of the detector event by event

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